982 PROTOZOA AND OTHER ANIMALS 



seldom been seen, and that ejected pieces are those with excessively 

 heavy membranes. Reichenow (in Doflein, 1927-29) did not agree 

 that it provides evidence against the use of cellulose, stating that Pro- 

 tozoa, especially when in unfavorable circumstances, may give up nutri- 

 ment useful to them. Usuelli (1930b) saw no microscopic indications of 

 corrosion of ingested fibers, and commented that in any case the green 

 plant fibers, that are the ones chiefly used, contain relatively little cellu- 

 lose. Westphal (1934a, 1934b) denied cellulose digestion in ophryo- 

 scolecids, and showed that, in spite of the presence of cellulose and 

 chlorophyll, cultures died out in the absence of starch. According to 

 Mangold, the colorless pieces persist for a long time, even for four days, 

 and during that time digestible substances are extracted. 



Earlier opinions that there is digestion of cellulose have been sum- 

 marized by Becker, J. A. Schulz, and Emmerson (1930). P. Schulze 

 (1924, 1927) and Trier (1926) believed that cellulose particles are 

 reduced chemically and structurally. Recently, Weineck (1934) ob- 

 tained positive evidence, including observations on corrosive changes 

 and loss of the original double reactivity in polarized light. 



No cellulose-splitting enzymes have been isolated from the bodies of 

 ophryoscolecids; that would be difficult in the presence of so many 

 cellulose-decomposing bacteria. It was the suggestion of Trier (1926), 

 and the opinion of Mangold (1929, 1933) and Westphal (1934a), 

 that bacteria taken in with plant fragments are responsible for what 

 cellulose decomposition has been observed within the ciliates. It is, of 

 course, well known that the main role, at least, in cellulose-splitting in 

 ruminants is performed by bacteria (Schieblich, 1929, 1932). If the 

 ciliate had a cellulase, according to Mangold (1929), more intensive 

 cellulose decomposition would be observed than has been possible. 



Doflein (Reichenow ed., 1927-1929) stated that there is no instance 

 of fat digestion in Protozoa. Ferber (1928) observed, in successive 

 rumen samples, that milk-fat droplets ingested in vivo underwent de- 

 formation and eventually disappeared, but he recognized the probability 

 that bacteria, ingested also, were responsible for this breakdown of 

 fat. Weineck, in experimental feeding with lipoids, found that no fat 

 was ingested, but he observed a small amount in the ciliates that probably 

 had been taken up from plant materials. 



Inasmuch as the ciliate population can be increased, up to a limit. 



